In this study, we focus on the intelligent behavior of an octopus and describe the development of a flexible manipulator. The manipulator is controlled by the dynamics of the body such as the flexibility of the sponges, resilience of the rubbers and constraint by the wires. By using the developed manipulator, we show that grasping behaviors and twisting behaviors similar to those of an octopus can be realized by the dynamics of the body without computation in its brain. Key Words : manipulator, octopus, many degrees of freedom, grasping.